Magnetic disk drives are used to store and retrieve data for digital electronic apparatus such as computers. In FIGS. 1A and 1B, a magnetic disk data storage system 10 of the prior art includes a sealed enclosure 12, a disk drive motor 14, one or more magnetic disks 16, supported for rotation by a drive spindle 18 of motor 14, and an actuator 20 including at least one arm 22, the actuator being attached to a pivot bearing 24. Suspensions 26 are coupled to the ends of the arms 22, and each suspension supports at its distal end a read/write head or transducer 28. The head 28 (which will be described in greater detail with reference to FIGS. 2A and 2B) typically includes a write element with a sensor read element. As the motor 14 rotates the magnetic disk 16, as indicated by the arrow R, an air bearing is formed under the transducer 28 causing it to lift slightly off the surface of the magnetic disk 16, or, as it is termed in the art, to “fly” above the magnetic disk 16. Alternatively, some transducers, known as contact heads, ride on the disk surface. Various magnetic “tracks” of information can be written to and/or read from the magnetic disk 16 as the actuator 20 causes the transducer 28 to pivot in a short arc across a surface of the disk 16. The pivotal position of the actuator 20 is controlled by a voice coil 30, which passes between a set of magnets (not shown) to be driven by magnetic forces caused by current flowing through the coil 30.
FIG. 2A shows the distal end of the head 28, greatly enlarged so that a write element 32 incorporated into the head can be seen. The write element 32 includes a magnetic yoke 34 having an electrically conductive coil 36 passing therethrough.
The write element 32 can be better understood with reference to FIG. 2B, which shows the write element 32 and an integral read element 38 in cross section. The head 28 includes a substrate 40 above which the read element 38 and the write element 32 are disposed. A common edge of the read and write elements 38, 32, defines an air bearing surface (ABS), in a plane 42, which can be aligned to face the surface of the magnetic disk 16 (see FIGS. 1A and 1B). The read element 38 includes a first shield 44, a second shield 46, and a read sensor 48 that is located within a dielectric medium 50 between the first shield 44 and the second shield 46. The most common type of read sensor 48 used in the read/write head 28 is the magnetoresistive (AMR or GMR) sensor, which is used to detect magnetic field signal changes in a magnetic medium by means of changes in the resistance of the read sensor imparted from the changing magnitude and direction of the magnetic field being sensed.
The write element 32 is typically an inductive write element that includes the second shield 46 (which functions as a first pole for the write element) and a second pole 52 disposed above the first pole 46. Since the present invention focuses on the write element 32, the second shield/first pole 46 will hereafter be referred to as the “first pole”. The first pole 46 and the second pole 52 contact one another at a backgap portion 54, with these three elements collectively forming the yoke 34. The combination of a first pole tip portion and a second pole tip portion near the ABS are sometimes referred to as the yoke tip portion 56. Some write elements have included a pedestal 55 which can be used to help define track width and throat height. A write gap 58 is formed between the first and second poles 46 and 52 in the yoke tip portion 56. The write gap 58 is filled with a non-magnetic, electrically insulating material that forms a write gap material layer 60. This non-magnetic material can be either integral with or separate from a first insulation layer 62 that lies upon the first pole 46 and extends from the yoke tip portion 56 to the backgap portion 54. The conductive coil 36, shown in cross section, passes through the yoke 34, sitting upon the write gap material 60. A second insulation layer 64 covers the coil and electrically insulates it from the second pole 52.
An inductive write head such as that shown in FIGS. 2A and 2B operates by passing a writing current through the conductive coil 36. Because of the magnetic properties of the yoke 34, a magnetic flux is induced in the first and second poles 46 and 52 by write currents passed through the coil 36. The write gap 58 allows the magnetic flux to fringe out from the yoke 34 (thus forming a fringing gap field) and to cross the magnetic recording medium that is placed near the ABS.
In order to increase data density it becomes necessary to decrease the size of the read and write elements 38, 32 of the head 28. By making the read and write elements 38, 32 smaller, the track width can be reduced and accordingly more tracks of data can be fit onto the disk 16. However, while decreasing the size of the head 28 the strength of the magnetic fringing field produced by the write element 32 must be maintained. One way of increasing the strength of the fringing field produced by a write element 32 is to use a high magnetic moment material in construction of the yoke 34. However, use of such high magnetic moment material presents certain challenges. For example, such high magnetic moment materials are highly corrosive. This problem is compounded by the high temperatures required to cure the coil insulation layer 64 and by the wet processes required for wafer fabrication. Such high temperatures cause any portion of high magnetic moment material exposed to atmosphere to quickly corrode. Wet chemicals may react with high magnetic moment material and cause corrosion. Prior art head manufacturing techniques require leaving the back gap portion 54 of the first pole 46 exposed to atmosphere so that the second pole 52 can be plated to connect with the first pole in the back gap 54.
Therefore, there remains a need for a method for constructing an inductive write element that makes use of the advantageous magnetic properties of high magnetic moment materials while mitigating the corrosion problems associated with such materials. Such a method would preferably be cost effective, requiring a minimum number of additional manufacturing steps and utilizing currently available wafer fabrication processes.